Josef brandstetter



1. BRANDSTETTER.

SOUND BOX. APPLICATION FILED FEB. 21. 1917.

Patented June 17, 1919.

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JOSEF BRANDSTETTER, OF ROCHESTER, MINNESOTA, ASSIGN'OR TO SEARS, ROEBUCK 8:

COMPANY, OF CHICAGO, ILLINOIS, A CORPORATION OF NEW YORK.

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Specification of LettersPatent. Patented J 111111119 1?, 1919,

Application filed February 21, 1917. Serial No. 150,188.

To all 'wlwm'z't may concern Be it known that I, J OSEF BRANDSTETTER, a subject of the Emperor of Austria-Hungary, residing at Rochester, in the county of Olmsted and State of Minnesota, have invented certain new and useful Improvements in Sound-Boxes, of which the following is a specification, reference being had therein to the accompanying drawing.

My invention relates to sound recording and reproducing or so called talking niachines and has for its object the improvement of sound boxes used therewith.

An object of my invention is to provide a sound box with improved means for tensioning the stylus lever and its bearings, whereby the bearings may be kept under sufficient tension to prevent chattering, and at the same time maintain ample flexibility in the tensioning of the said lever to prevent over-damping of its vibrations of high amplitude.

Another object of my invention is to provide a symmetrical means for tensioning both the bearings and the stylus lever, arranged to automatically maintain a substantially constant ratio between the tension on the bearings and the tension on the said stylus lever throughout various adjustments,

and also to act always in the plane in whichv the stylus lever vibrates, and [perpendicularly to the axis around which said lever vibrates.

' Other objects of my invention reside in the novel construction, combination and arrangement of parts hereinafter described and particularly pointed out in the appended claims.

My invention is illustrated in the accom panying drawings in which I Figure 1 is a front elevation of my improved sound box.

Fig.2 is a side elevation of the same partly in transverse section.-

"Fi 3 is a bottom plan view with the stylus set screw removed.

Fig. i is a bottom plan view of the hearing yoke carrying the stylus lever.

Figs. 5 and 6 are detail views of one of the tensioning springs.

' Referring to the drawings in detail, 1 indicates the body portion of the sound box proper consisting of the annular side wa1l2, back wall 3, and flange or neck portion 4.

A fiat surfaced mounting lug 5 is formed on the lower edge of the sound box body and hasa pair of knife edges 6 and 7 secured thereto. The diaphragm 8 of mica or other equivalent material is suitably mounted within the sound box, as between a pair of tubular rubber gaskets 9 and 10, the inner gasket 9 being partially countersunk or nested into an annular recess 11 in the back wall 3 of the sound box body. These gaskets are held in place and compressed as shown in Fig. 2-by means of the retaining ring 12 threaded on its periphery to engage complementary threads at 13 on the inner surface of the armular side wall 2, the proportions of the diaphragm and sound box cavity being such that, when the ring 12 is screwed in flush with the front surface of the sound box, the gaskets will be compressed to hold the diaphragm resiliently and without lost motion there'between, spaced away from the back wall of the sound box and with a slight clearance between the periphery of the diaphragm and the side Wall of the sound box at 14. As an alternative construction, the ring 12 may be laid fiat on or within the edge flange of the box and screws tapped through it into the body of the box. This is in some respects a preferred construction, as by using a number of screws around the ring, it enables adjustment to be made of the pressure on different parts of the gaskets and diaphragm. A stylus lever 15 connected to the diaphragm at 16 is carried by the bearing yoke 17 which is provided with a shallow trough or depression at each end, 19 and 20, in which seat I the knife edges 6 and 7 respectively. The bearing yoke 17 carries a pair of tensioning arms 21-22 extending at right angles therefrom in opposite directions and in the longitudinal plane of the stylus lever; and extending downwardly from the yoke and p0- sitioned centrally thereof is a stylus holder 23 which is provided with the usual socket 24 and knurled set screw 25 for holding the stylus point 26, the parts being so arranged as to bring the stylus point approximately in the li ne of intersection of the perpendicular planes passing through the diaphragm and the stylus lever.

For holding the knife edge bearings seated and tensioning the stylus lever, I provide a pair of how springs 28 and 29 secured and tensioned by adjusting screws 27 and 31 respectively, threaded into the mounting lug loo 5. These springs are arranged with rela tively short and long fin ers 3032 and 33-34, which respectively ear on the ends of the yoke directly under the knife edges and on the ends of the tensioning arms 32 and 29. In order to prevent these tensioning springs from turning about the adjusting screws, I provide the ends of the tensioning arms yvith downwardly projecting pins which pass through holes or slots 35-36 in the ends of the long fingers of the springs. Between the ends of each spring finger and the point where it engages its yoke or tensioning arm, I place a small contact pad, 37-38, of suitable resilient material such as rubber, the pads 37 being held in place by small indentations 39 in the ends of the yoke into which a portion ofthe pad extends under pressure of thespring, and the pads 38 being held in place by means of the downwardly projecting pins which pass through the slots 35-36. A sharp bend or dip 40 is formed at the end of each spring at the point of engagement with the pad to reduce the area of the contacting surface to a narrow zone running transversely of the spring so as to permit a slight rocking motion between the ends of the spring fingers and the pads without substantially varying the leverage of the spring fingers. It will be readily seen from the drawings that the tension of the springs can be accurately adjusted by means of the screws 273l, which may be set at any adjustment by means of the lock-nuts 4.-142.

By the arrangement of the tensioning! springs as here shown and described, the same set of springs is used both for holding the bearings firmly seated and for tensioning the stylus lever, at the same time alfording a, sufficient pressure on the bearings to prevent their chattering without exerting an undue pressure on the stylus lever. I obtain this difference in pressure between the different ends of the same springs by making the springs with long and short fingers as shown in Fig. 3 and arranging them so that the short fingers will bear upon the ends of the yoke directly opposite the knife edges 6 and 7, and the long fingers, 32-34, upon the ends of the adjusting arms 21-22. Thus with any adj ustmentof the tension of the springs 28 and 29 this ratio will obtain,

so that the higher pressure for holding the knife edges seated will be proportional to the amount of force required to oscillate the stylus lever. By making the stylus lever tensioning fingers 3234: proportionately long, I not only get a reduction in tension, but an increased flexibility or amplitude of flexure, which while far in excess of that required by the very slight movement of the stylus lever, has the advantage of making theresistance offered throughout this movement substantially constant as will be readily understood, thus overcoming the tendency to over-damp vibrations of higher amplitude,

and giving a truer reproduction of the 'origi- I to the usual'amplifying means, I provide a bushing l5 of rubber or equivalent sound insulating material within the sound box neck 4:, which bushing is so proportioned as to fit snugly over the end of the tone arm. Communication between the diaphragm 8 and the interior of the neck 4 is had by an aperture 46 in the back wall of the sound box.

Some changes of detail, design, proportions and arrangement can be made herein without departing from my invention. I contemplate as my own any such changes as fall within the scope of the appended claims.

Having thus described my'invention what I claim and desire to secure by Letters Patent is:

1. In a sound box, the combination of a diaphragm, a stylus lever connected thereto and carried by a transverse yoke mounted to oscillate on knife bearings, and resilient tensioning means arranged to bear on the yoke at points lying outside of the axis of said bearin and in a plane passing through the stylus lever and its connection with the diaphragm and perpendicular to the said axis to tension said stylus lever in opposite directions, whereby the opposing forces exerted by the diaphragm and the tensioning means respectively will act in a common plane perpendicular to the axis of oscillation.-

2. In a sound box, the combination of a diaphragm, a stylus lever connected thereto and carried by a transverse yoke mounted to oscillate on knife edge bearings, a pair of tensioning arms carried by the yoke extending in opposite directions in the plane passing through the stylus lever and transverse to the axis "of said bearings, and resilient means acting on both the yoke and said arm to maintain the said bearings seated and to tension the stylus lever in opposite directions through said tensioning arms.

3. In a sound box, the combination of a diaphragm, a stylus lever 'connected thereto and carried by a transverse yoke mounted to oscillate on knife edge bearings, and resilient means bearing on said yoke at points over said bearings to maintain the same seated and also at points spaced from the axis of said bearings in the plane of oscillation of the stylus lever, transverse to said axis to tension said stylus lever in opposite directions.

4. In a sound box, the combination of a. diaphragm, a stylus lever connected thereto and carried by a lilitnS"BIS( yoke mounted to oscillate on knife edge bearings, a pair of and at a point on one of said tensioning arms to tend to oscillate the said yoke and stylus arm on the bearings.

5. In a sound box, the combination of a diaphragm, astylus lever connected thereto and carried by a transverse yoke mounted to oscillate on knife edge bearings, a pair of tensioning arms carried by the yoke extending in opposite directions in the plane of the stylus lever and transverse to the axis of said hearings, and a pair of tensioning springs each held fixed at a point intermediate its lengthand hearing at its opposite ends upon said yoke at a point opposite one of said hearings to maintain the same seated and at a point on one of said tensioning' arms to tend to oscillate the said yoke and stylus arm on the bearings, the point at which each of said springs is held fixed being so located with respect to the ends of the spring as to cause a greater pressure to be exerted upon the knife edge bearing than so upon the tensioning arm.

In testimony whereof I affix my signature.

J OSEF BRANDSTETTER. 

